Glass mirror



(No Model.)

J. M. GONROY & F. E. YOUNGS.

. GLASS MIRROR; No. 290,744. Patented Dec. 25, 1883.

WFLEESR Y [qveqlnaa M 5;, ym J jy y" silver in contact with the glass.

STATES PATENT rrrcn.

JOHN M. CONR-OY AND FRED E. YOUNGS, OF ALLEGHENY, PENNSYLVANIA.

GLASS MIRROR.

SPECIFICATION forming part of Letters PatentNo. 290,744, dated December25, 1883.

To all whom it may concern.-

Be it known that we, JOHN M. CONROY and FRED E. YoUNGs, of the city ofAllegheny, in the county of Allegheny and State of Penn sylvania, haveinvented a new and useful Improvement in Glass Mirrors; and we do herebydeclare the following to be a full, clear, and exact descriptionthereof.

The silver deposited on the surface of sheets or plates of glass, forthe purpose of making mirrors, is very apt to suffer injury bymechanical abrasion, and also by oxidation from the access of theatmosphere. In order to protect the silvered surface from being defacedby either of these causes, it has been suggested to coat the silveredsurface of the glass with a thin film of copper deposited on the silverby the electrotype process; but this method, although affording acertain degree of protection, is liable to two serious objections,either of which renders it practically useless. The first of these isthat the contact of the two metals causes a galvanic action to beestablished,which in process of time causes the silver to be so acteduponas to destroythe smoothness of its surface, and thus render ituseless as a mirror; and the other is that, owing to the differentdegrees of expansibility by heat of copper and silver, the continuity ofsurface of the silver is broken up by the formation of minute cracks,with a like in jurious effect on the mirror. In both cases, also, themirror becomes spotted and discollored, owing to the access of oxygen,and in some localities of sulphur, to the surface of the Another methodwhich has been proposed is to coat the outer surface of the silver witha film or succession of films of varnish, paint, or like substances; butthis is liable to the objection that these substances will graduallyshrink and crack and expose the silver to the oxidizing effect of theatmosphere.

The method of protecting the silvered surfaces of mirrors which we haveinvented is designed to obviate these defects by coating the outersurface of the silver, after it has been deposited upon the glass, witha thin film of wax, paint, varnish, or similar substance, and thenapplying an exterior coating of metal, by which means we not onlyprotect the silver deposited on the glass from being Application filedAugust 18, 1883. (No model.)

attacked by the oxygen and sulphur in the atmosphere, but also obviatethe injurious effects resulting from the immediate contact with:

the silver of another metal.

In order to enable our invention to be used by others skilled in theart, we will proceed more fully to describe the method by which we carryit into effect.

The glass having been first coated with silver by. any of the methodsused for that purpose, a thin film of wax, varnish, paint, or similarsubstance is applied, the manner of its application depending on thesubstance used. For this purpose it is desirable to use a. sub stancewhich contains as little oxygen as possible. Beeswax or any of thevegetable or mineral waxes may be employed, in which case theplate-glass may be heated in any convenient mannerto a sufficient degreeto melt the wax, which is then gently rubbed over the surface of thesilver until it is uniformly coated therewith.

In place of wax, any suitable paint or varnish may be used, or theviscous residuum of the distillation of petroleum, which, if reduced toa sufficient degree of consistency, is

desirable as being free from oxygen. Before the film thus appliedbecomes hard a thin leaf of metallic foil is placed evenly on thesurface of the plate, over the film of wax or other substance, and ispressed down closely by means of a roller, brush, or otherwise, so as toform a close union between the foil and the film of wax or othersubstance, and to exclude all bubbles of air.

If the inner coating is made of wax or other substance which willbecome, when cold or dry, sufficiently hard to permit of it, the outeror metallic coating may be applied by first coating the surface of thewax, &c. with plumbago, and then depositing a film of copper, tin, orother metal by means of the electrotype process in the well-known method5 or, if preferred, the metallic coating may be applied by means offoilsuch as tin-foil-0r of paper coated with silver or other metal, inwhich case we prefer to apply the metallic surface of the paper to thesurface of the inner coating.

Having thus described our improvement, what we claim as our invention,and desire to secure by Letters Patent, is-

1. The method hereinbefore described of protecting the silvered surfaceof mirrors from abrasion and atmospheric action by applying to theexterior surface of the silver an inner coating of wax or other suitablesubstance and 5 an outer coating of metal, substantially as and for thepurpose described.

2. As a new article of manufacture, silvered glass mirrors having on thesilvercd surface an inner coating of wax or other similar sub- 10 stanceimpervious to the atmosphere and an outer coating of metal,substantially as de scribed.

In testimony whereof we have hereunto set our hands this 15th day ofAugust, A.D.1883.

JOHN M. CONROY. FRED E. YOUNGS.

Witnesses:

THOMAS W. BAKEWELL, W. B. CoRWIN.

